The role of aerosols in atmospheric chemistry has recently become of great interest, because relatively little is known regarding the reactivity and transport of environmental aerosols. The catalytic effect of aerosol particles in heterogeneous (gas-particle) reactions occurring in the atmosphere is known to depend on both the particle's surface area and the particle's chemical composition.
Aerosol characterization also can be important in the medical and industrial fields. Great efforts have been made to study the effects of particles in biological systems, particularly on the human lungs and cardiovascular system. Although carcinogenicity and toxicity both depend on chemical composition, the chemical will have little influence on the body unless it is in some way retained. Particles ranging from ultrafine (<100 nm) up to 10 microns are of interest because they are the most likely to serve as carriers of toxic chemicals and to be deposited in some part of the human body (i.e. lungs, bloodstream, liver, heart, brain) for significant time durations. Due to health concerns, industries that require employees to operate in dust-laden environments, e.g., mines, also are interested in aerosol characterization. Further, may need to determine the contents of the air to maintain clean semiconductor devices.
In addition, the ATOFMS can be designed to identify various biological particles and sources including single cells and microorganisms. For example, specific cell (e.g., cancer cell) can be identified among a tissue sample to identify a target of pharmacological agents and to confirm that enough of the cancer cells were removed during surgery (pathology application).
Mass spectrometry is a technique for analyzing many types of environmental and biological samples, including aerosols. When combined with some means to determine particle size, mass spectrometry can provide means for determining both the size and chemical composition of particles in a polydisperse sample. Mass spectrometers generally include the following four basic steps as part of their analysis: 1) sample introduction; 2) sample volatilization and ionization; 3) mass separation; and 4) ion detection. Numerous routines can be used to perform each of these steps, although not all may be compatible with aerosol characterization. Sample introduction into a mass spectrometer for aerosol characterization can be performed in one of following two ways: (1) placing the sample on a surface, or (2) forming a particle beam by free jet expansion into a vacuum. Sample volatilization and ionization in the case of aerosol mass spectrometric analysis can utilize any of numerous suitable techniques, including, for example, laser desorption/ionization. Mass separation also can be accomplished using any of multiple techniques, including, for example a time-of-flight mass analyzer. Finally, ion detection can be accomplished using, for example, microchannel plate detectors.